Renal biopsy is an essential and indispensable technique for diagnosing kidney diseases, especially glomerular disease which induces protein-losing nephropathy. However, renal biopsy is invasive and should not be performed without careful consideration. In addition, the pathological diagnosis of glomerular disease requires not only general light microscopic observations but also electron microscopic and immunofluorescent analyses, and it requires adequate knowledge for handling the collected kidney tissues. This article describes the anatomy of the kidney and sampling methods, as well as the tissue handling to lead to an appropriate pathological diagnosis.

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A cat with acute kidney injury following anesthesia presented with pleural effusion and pulmonary edema. Echocardiography revealed cardiac enlargement and cardiac hypertrophy. The patient was treated with hemodialysis for acute kidney injury and survived the acute phase. After renal function recovered, echocardiography showed improvement of cardiac enlargement and cardiac hypertrophy. Based on these findings, the patient was considered to have acute renocardiac syndrome.

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Feline kidney disease is increasing in clinical practice. Staging of chronic kidney disease follows the criteria of the International Renal Interest Society (IRIS); i.e., based on plasma creatinine and symmetric dimethylarginine (SDMA). Plasma creatinine is affected by non-renal factors, including gender, age and muscle mass, whereas SDMA is known to increase after loss of >40% of glomerular filtration rate. In this study, we examined plasma glycoproteins as early diagnostic markers for chronic kidney disease and identified fucosylated apolipoprotein A-IV as such a marker.

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Serum creatinine concentration, the classical biomarker of chronic kidney disease (CKD) in cats, has important limitations that decrease its value as a biomarker of early CKD. Recently, serum symmetric dimethylarginine concentration was introduced as a novel glomerular filtration rate biomarker for the early detection of CKD in cats. However, data on its specificity are still limited. The limitations of conventional biomarkers and the desire for early therapeutic intervention in cats with CKD to improve outcomes have prompted the discovery and validation of novel renal biomarkers to detect glomerular or tubular dysfunction. Changes in the serum or urinary concentrations of these biomarkers may indicate early kidney damage or predict the progression of kidney before changes in conventional biomarkers are detectable. This review summarizes current knowledge on renal biomarkers in CKD in cats, a field that has progressed substantially over the last 5 years.

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[in Japanese]

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